“My neighbour got permission for exactly the same extension. Why was mine refused?”
It’s one of the most frustrating experiences in the planning process. Your neighbour builds a two-storey rear extension or a dormer loft conversion, so you submit what appears to be the same proposal, only for the Local Planning Authority (LPA) to refuse your application. How can that happen?
It can feel inconsistent, but the UK planning system doesn’t work on a “copy and paste” basis. Every planning application is assessed on its own merits, taking into account the specific site, the design of the proposal, current planning policies, and any constraints affecting the property. As a result, two proposals that look almost identical can receive very different decisions.
Many homeowners assume that if a neighbour has received planning permission, the council must approve theirs as well. Unfortunately, that’s a common misconception. While nearby approvals can sometimes provide useful context, they do not set a precedent that the council is legally required to follow. A large part of the decision comes down to the individual characteristics of each site.
Even neighbouring houses on the same street can have different physical constraints. They may look identical, but the relationship with surrounding buildings, neighbouring windows, ground levels, boundaries, or garden depths can all influence the planning assessment.
For example, imagine two semi-detached houses proposing the same rear extension. One is approved because it sits alongside a neighbour’s blank garage wall. The other proposes exactly the same extension, but it would run alongside the main living room window of the adjoining property. Although the extensions are physically identical, their impact on neighbouring amenity is very different.
This is why planning decisions are influenced by the site’s characteristics rather than simply the size or dimensions of the proposal. Protecting the living conditions of neighbouring occupiers is a fundamental objective of the planning system, and officers carefully assess whether a development would cause unacceptable harm through overlooking, overshadowing, or an overbearing sense of enclosure.
Apart from size, there is also the quality of design. Homeowners often focus on measurements, but planning officers are usually asking questions such as:
Planning is rarely just about meeting dimensional limits. It’s also about how the proposal has been designed and how well it responds to its setting.
Alongside site-specific constraints, planning officers also assess whether a proposal respects the prevailing character and appearance of the surrounding area. A design that works well in one location may feel completely out of place somewhere else.
For example, you might propose the same contemporary brick extension that your neighbour built last year. Their property, however, sits beside a modern apartment building, so the design complements its surroundings. Your house, on the other hand, may sit between traditional brick homes with pitched roofs and red clay tiles. Without changing the design at all, the extension could appear out of scale, disrupt the established street scene, or fail to reflect the area’s character. The proposal hasn’t changed, but its context has.
Another reason similar applications receive different outcomes is that planning policy evolves over time. What was considered acceptable a few years ago may not necessarily be supported today.
Local authorities regularly update their Local Plans and Supplementary Planning Documents (SPDs), introducing revised guidance on design, privacy, residential amenity, and other planning matters. National policy also changes. Updates to the National Planning Policy Framework (NPPF), particularly around sustainability, biodiversity, and housing delivery, can influence how planning officers assess proposals.
Because policies evolve and every site has its own constraints, planning is rarely a straightforward checklist exercise. Many policies rely on terms such as appropriate, proportionate, subordinate, or harmful. Applying those policies requires professional judgement, with officers weighing both the benefits and the impacts before reaching an overall planning balance.
Two similar proposals can receive different outcomes because they differ in how they respond to their surroundings, comply with policy, or affect neighbouring properties, not because the planning system is inconsistent.
When planning for extensions, we may look at nearby planning approvals for inspiration and possible extent, but this should not be treated as assured guarantees. Every planning application is assessed on its own merits, considering the unique characteristics of the site, the design of the proposal, the surrounding context, current planning policy, and any other material planning considerations.
Before investing in detailed design work or relying on a neighbour’s approval, it is worth asking planning professionals regarding your site-specific constraints, or planning appraisal. A proposal that appears similar on paper can perform very differently when assessed against the planning policies and constraints that apply to your own property.
For expert assistance and to ensure your proposal is robust, visit https://massandstrategy.co.uk/ for professional planning appraisals.
